1. Field of the Invention
The present invention relates to a rechargeable battery having an improved structure of a current collecting plate electrically connected to an electrode assembly.
2. Description of the Related Art
Rechargeable batteries can be repeatedly charged and discharged, unlike a primary battery that is incapable of being recharged. A low capacity rechargeable battery composed of a single cell is generally used for a portable small electronic device, such as a mobile phone, a laptop computer, and a camcorder. A large capacity rechargeable battery composed of a plurality of cells connected in a form of a pack is widely used to drive a motor for a hybrid electric vehicle. Such rechargeable batteries are serially connected to form a rechargeable battery module to drive a motor for an electric vehicle, which needs a large amount of electric power.
Such a rechargeable battery is manufactured in various forms. The representative form of a rechargeable battery is a cylindrical form or a quadrilateral form. The rechargeable battery includes an electrode assembly having an anode and a cathode with a separator interposed therebetween, a case for providing a space for housing the electrode assembly, and a cap assembly for closing and sealing the case.
In the case of a rechargeable battery formed in a cylindrical shape, an uncoated region, where an active material is not coated, are formed in the anode and the cathode of the electrode assembly, and a positive uncoated region and a negative uncoated region are disposed to face in different directions.
A cathode current collecting plate is adhered on the negative uncoated region and an anode current collecting plate is adhered on the positive uncoated region. The cathode current collecting plate is electrically connected to the case, and the anode current collecting plate is electrically connected to the cap assembly to allow current to pass to the outside. Therefore, the case is operated as a negative terminal, and the cap plate mounted in the cap assembly is operated as a positive terminal.
Since the anode current collecting plate and the cap assembly are electrically connected by a lead member made of a conductive metal, the lead member, the anode current collecting plate, and the cap assembly are welded together and then inserted into the case. After the cap assembly is inserted, the cap assembly is fixed to the case by clamping the cap assembly.
Since current is drawn out to the outside through the current collecting plate that is electrically connected to the electrode assembly, it is very important to have a stable connection between current collecting plate and the electrode assembly.
In the case of a high power battery, high current flows through the current collecting plate. Therefore, the smaller the resistivity of the current collecting plate, the more current loss can be reduced. Accordingly, it is preferable to form the current collecting plate to have a large thickness. However, if the thickness of the current collecting plate is too thick, heat is not fully transferred to the electrode assembly and so it is difficult to weld the current collecting plate to the electrode assembly.
Conventionally, the current collecting plate and the electrode assembly are simply welded together at a surface contact of the current collecting plate and the electrode assembly. Since no structure supports the current collecting plate in a side direction, the contact between the electrode assembly and the current collecting plate becomes poor weak an external impact is applied. If the contact between the current collecting plate and the electrode assembly becomes poor, the resistivity around the contact increases. Therefore, the output of the rechargeable battery becomes reduced and the rechargeable battery generates a large amount of heat. What is therefore needed is an improved design for a rechargeable batter where the contact between the electrode assembly and the current collecting plate that is strong and reliable enough to withstand various forms of impact.